The referencing section is a tenancy assessment report which is similar to a credit check (it's not possible to credit check a tenant because no credit is being provided).
Accessing the new referencing can be found here: https://docs.landlordsguild.com/referencing
The tenancy assessment report checks public data such as:
Electoral roll check at the applicant’s current and previous addresses.
A tenancy assessment score, predicting the applicant’s likelihood to pay.
A Public Information check to ascertain whether the applicant has CCJs, bankruptcy orders or voluntary arrangements.
A check to see if the applicant has any undisclosed addresses.